Bill Donohue, president of the conservative Catholic League, says he was forced to reverse course on marching in this year's annual New York City Gay Pride parade.

Donohue, an ardent opponent of gay rights, is pursuing a boycott of Guinness over the beer company's decision to withdraw its support from New York City's St. Patrick's Day parade over the parade's exclusion of gay groups.

(Related: Bill Donohue calls on Catholics to boycott beer companies over pro-gay stance.)

Last week, he applied to march in June's Gay Pride parade under a “Straight is Great” banner.

NYC Pride responded in a press release that Donohue and his group “are free to participate in the 2014 March.”

But on Friday, Donohue backed out, claiming organizers were forcing him to attend “gay training sessions.”

“Today, I informed Heritage of Pride officials that I objected to their rule requiring me to attend gay training sessions, or what they call 'information sessions,'” Donohue said in a blog post. “'I don't agree with your rule,' I said. They responded by saying that attendance was 'mandatory.'”

“It is hypocritical for gay activists to complain about having to abide by the mandatory rules of the St. Patrick's Day parade, and then inform me that I cannot march in their parade unless I respect their mandatory rules, rules that I reject,” he said.

“Good luck to the Heritage of Pride participants. I may be watching it from far, but I sure won't be downing a Guinness afterwards,” he added.